Saliva is the principle protective agent for the mouth and thus is of primary importance to oral health maintenance. Perturbations in the salivary secretory mechanism can consequently lead to serious oral health problems. The objective of this project is to study the membrane and cellular processes which underlie the phenomenon of primary fluid secretion by salivary acinar cells and thus to contribute to our understanding of the fluid secretory process in normal and diseased states. Because similar secretory mechanisms are thought to be common to a number of other exocrine glands, this information should be of rather broad applicability and interest. During the present reporting period our specific areas of focus were the following. (1) The transport of ions (Na+, K+, Cl-, TcO4-), whose transmembrane and transepithelial movements are thought to be related to the process of primary salivary fluid secretion, was studied in vitro in a rat parotid acinar suspension and/or in isolated rabbit parotid basolateral membrane vesicles. These transport studies concentrated primarily on the properties of a basolateral Na/K/Cl cotransporter thought to be primarily responsible for producing the ion gradients which drive fluid secretion. (2) The binding of a specific inhibitor of the Na/K/Cl cotransporter, [3H]-bumetanide, to rabbit basolateral membrane vesicles was characterized. (3) Procedures for isolating parotid acinar luminal membrane vesicles, and for improving existing basolateral membrane vesicle preparations and acinar suspensions were developed.